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Changing from two drives in RAID 1 to four drives in RAID 5

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May 6, 2012 10:02:41 PM

I am working with a PowerEdge T110 server with Windows Server 2008 R2. It currently has two drives configured in a RAID 1. I want to replace those drives with four new drives in a RAID 5. The current drive has a number of virtual drive letters for network purposes that I want to preserve.

What is the best procedure for doing this?
a c 289 G Storage
May 8, 2012 1:02:05 PM

1) Build the RAID5 in the machine while it still has the RAID 1.
2) Create the same partitions on the RAID5 as the RAID1 has. If you don't know how to see this and duplicate it, we will tell you.
3) Copy the data from the old array to the new
3) Use a diff tool to ensure that they match
4) Dismount and decommission the old array. Change the drive letters on the new one.

Seriously, the best option is to copy the data, not try to "migrate." If you don't have room for both arrays at once, then make a backup of the first array, test it, take out the first array, build the second, and restore the backup.

Again, let us know if you need help with the drive letters issue.
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May 8, 2012 5:03:20 PM

I will have to take the second option because the T110 can only take 4 drives at a time. The new array will take up all 4 available slots.

I will make a backup of the current array and restore it to the new. This probably means I will need to reinstall the OS, right? Or will an image backup of the current array preserve the OS?

Also, I'm confused about the "partitions" because they don't appear as partitions in disc management. They have drive letters, but I think they are some other kind of mapped network folders or something. I don't know what they are, but they are not genuine disc partitions. I'll send a screen shot later today.
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a c 289 G Storage
May 8, 2012 5:31:47 PM

Oh, dear. Is the OS on the RAID, too? In that case, I am not really qualified to answer.
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May 8, 2012 8:18:54 PM

I'm fairly certain it is. There are only two disks in the RAID 1 array, and the OS is definitely on those discs.

You're making me very nervous, is this unusual?

My tentative plan is to make an image backup of everything including the OS and hope it simply copies onto the new RAID 5 array.

Plan B is to have the Windows recovery disc ready in case I need to reinstall the OS onto the new array, then copy everything else onto the new array.

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a c 289 G Storage
May 8, 2012 8:25:12 PM

"You're making me very nervous, is this unusual?" I don't know, are you usually a calm person?

I only ruled myself out because I have never run an OS from a RAID drive, so I don't have the experience. If I had to guess, I would guess that restoring an image backup of the RAID 1 set to the newly-built RAID 5 set will boot and run, but I have no experience to prove it. As far as I know, the same drivers will handle a RAID 5 set that would handle a RAID 1 set.

Wait and see if someone who has actually done this wanders by.

EDIT: let me put it this way. I would try it with my own PC. I would not try it with a production machine, because the need to rebuild would be less acceptable.
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May 8, 2012 8:43:09 PM

Thanks WyomingKnot.

Just to be clear, I want to totally remove the current drives and start fresh with 4 new 2tb drives in a RAID 5 array.

I'm guessing I will need the OS recovery disc when I first boot with the new discs in place. Will the OS recovery disc give me the opportunity to recover from an image backup? Will it be able to recover the backup from an attached USB drive?

It's amazing how much I don't know even though I thought I knew quite a bit :~)

Sorry for any dumb questions, I just haven't done this before and I'm particularly nerved up because it's a small business server and I need to have a high level of confidence before I dive in.
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May 21, 2012 1:20:54 AM

Well I finally got it done. It was complicated because Dell's cruddy technical support gave me bad info which I'll skip explaining here.

For reasons passing understanding RAID is unavailable in UEFI boot mode, but it was very easy to create two virtual RAID 5 discs in BIOS mode. One had to be small for the OS because an MBR can't be bigger than 2.2tb. So I simply made the second virtual disc the size of the remaining space and converted it to a GPT dynamic disc in disc manager from the OS. So now I have a small 100gb C drive for the OS and the remaining 5.6tb is the D drive.

Concerning the backup, I simply did a file backup and NOT an image backup. then copied it onto the D drive after re-deploying the OS.

It's up and running now and working great, but I'm only getting about 50-60mbps read and write. For writes that seems reasonable, but for reads on a 4 disc RAID 5 that seems really slow. Are my expectations too high, or could something be out of order that could be tweaked or otherwise fixed to improve those read speeds?
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Best solution

a c 289 G Storage
May 21, 2012 12:55:03 PM

Congrats on getting it working. RAID speeds are beyond my experience, so I suggest you start another thread and grab someone with more experience.

The only reason for doing an image backup would be to let you boot off the restored OS, so file backup is just fine for data, as you figured out for yourself.
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May 22, 2012 4:30:57 AM

Best answer selected by mojoman317717.
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